Answer:
4/3 m/s
Explanation:
Assuming momentum is conserved, the sum of products of mass and speed before the collision is the same as after:
(2000 kg)(4 m/s) +(4000 kg)(0 m/s) = (2000 +4000 kg)(Vt)
Vt = (8000 kg·m/s)/(6000 kg) = 4/3 m/s
The speed of the combined objects after the collision is 4/3 m/s.